Most physiological functions of the mammalian body are controlled by enzymes or hormones which may be generically described as physiological catalysts. Many of these involve metabolic reaction sequences, one or more steps of which involve hydrolytic cleavage of a protein. For example, in the sequence of reactions which results in the coagulation of blood, a critical step is the conversion of prothrombin to thrombin. This conversion is catalyzed by the enzyme Factor X.sub.a, which stimulates the hydrolysis of arginylthreonine and arginylleucine depeptide units in the prothrombin molecule.
If these proteolytic control cleavage steps go awry, there may be unfortunate pathological results. For example, the body protects itself from the danger of circulating blood clots by dissolving them. A part of the reaction sequence which ultimately effects such dissolution is the conversion of plasminogen to plasmin which is triggered by the enzyme urokinase. Excess urokinase activity can result in the formation of too much plasmin, and this, in turn, can lead to inability to form clots. Consequently, the body is unable to protect itself from hemorrhage. There are many other examples of such metabolic malfunctions.